Avast Thar Geo,
From what Aye have been able to gather, the best way to connect a PC to a Zendrum is through some sort of audio interface. The best that I can tell is the the Motu Hybrid Mk III, but it is expensive. M-Audio has worked some deals with ProTools and offers a combo package. Aye use a Presonus USB Audio Interface because it was a less expensive alternative to the Motu and M-Audio units, but it has its drawbacks. Hope this helps.
Fair Winds and following Seas,